Re: port forwarding without the shell
From: Rachan Malhotra (rMalhotra_at_freightdesk.com)
Date: Wed, 23 Jun 2004 00:21:23 -0400 To: Andrius Kurtinaitis <email@example.com>
The -N option allows you to only fwd ports and not do anything else. You
can use it with -f to run your process in the background. I recently
used Autossh (http://freshmeat.net/projects/autossh). It is a wrapper
that allows you to create an always-alive tunnel in the background. You
may want to see if you can it put to use.
The drawback with -N is that it works from client side. I'd like to know
if there is a server side option to restrict (some) users so that they
can only connect to the ssh server for port fwding..
Andrius Kurtinaitis wrote:
> is it possible to do "one-shot" port forwarding if I do not have any
> valid shell on the ssh server, I can only use it for port forwarding.
> I read, that the normal way is to use -f and sleep 10. But I can not
> sleep because I do not have any shell on the server side...
> Another question is - how can I start the port forwarding in the
> The problem is that openSSH requires a command if I want to use the
> option -f ("Cannot fork into background without a command to
> execute."). If I give some dummy command like "sleep 10", it sends it
> and gets reply immediately (because there is no shell on the server)
> and exits immediately...
> On the client side of ssh I use debian sarge or unstable
> (OpenSSH_3.8.1p1 Debian 1:3.8.1p1-4, OpenSSL 0.9.7d 17 Mar 2004).
> On the server side, I suspect, there is also some linux with openSSH,
> maybe Red Hat.
> Andrius Kurtinaitis